Tag: astronomy

Week long movie of Pluto produced by New Horizons

10:28 pm

Cool images! Using New Horizons’ long range camera scientists have compiled a movie showing Charon and Pluto orbiting each other during the last week of January 2015.

Pluto and Charon were observed for an entire rotation of each body; a “day” on Pluto and Charon is 6.4 Earth days. The first of the images was taken when New Horizons was about 3 billion miles from Earth, but just 126 million miles (203 million kilometers) from Pluto—about 30% farther than Earth’s distance from the Sun. The last frame came 6½ days later, with New Horizons more than 5 million miles (8 million kilometers) closer.

The wobble easily visible in Pluto’s motion, as Charon orbits, is due to the gravity of Charon, about one-eighth as massive as Pluto and about the size of Texas.

Our view of Pluto, and Charon, is only going to get better as New Horizons zooms towards its July fly-by.

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Astronomers find an invisible dwarf galaxy

10:05 am

Using dark matter data that suggested the existence of a faint dwarf galaxy 300,000 light years away on the other side of the Milky Way, astronomers have pinpointed its location by finding a tiny cluster of bright Cepheid variable stars, also located at that distance.

“These young stars are likely the signature of this predicted galaxy,” said Chakrabarti, assistant professor in RIT’s School of Physics and Astronomy. “They can’t be part of our galaxy because the disk of the Milky Way terminates at 48,000 light years.” Invisible particles known as dark matter make up 23 percent of the mass of the universe. The mysterious matter represents a fundamental problem in astronomy because it is not understood, Chakrabarti said.

This result is intriguing because it not only found a previously unknown dwarf galaxy orbiting the Milky Way, it also provides further evidence that dark matter, whatever it is, does exist. The dark matter of this unseen dwarf galaxy showed its gravitational effects on Milky Way stars, and when the astronomers looked at the right spot suggested by those effects, they found distant stars that had to belong to the invisible dwarf galaxy, proving it was there. This is comparable to finding Neptune and Pluto by analyzing their gravitational effects and then predicting their location in the sky.

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The Hubble Space Telescope lives on!

8:18 pm

At a press conference at the January meeting of the American Astronomical Society scientists and engineers of the Space Telescope Science Institute that operates the Hubble Space Telescope reported that it is functioning far better than expected and is likely to continue to function until 2020 or beyond.

This is good news, since there is nothing being planned to replace Hubble. The article implies that the James Webb Space Telescope has that job, but Webb is an infrared telescope, not optical, and thus observes the universe in wavelengths not visible to the human eye.

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Gravitational wave/inflation discovery literally bites the dust

9:24 pm

The uncertainty of science: The big discovery earlier this year of gravitational waves confirming the cosmological theory of inflation has now been found to be completely bogus. Instead of being caused by gravitational waves, the detection was caused by dust in the Milky Way.

Even while the mainstream press was going nuts touting the original announcement, I never even posted anything about it. To me, there were too many assumptions underlying the discovery, as well as too many data points with far too large margins of error, to trust the result. It was interesting, but hardly a certain discovery. Now we have found that the only thing certain about it was that it wasn’t the discovery the scientists thought.

Nor is this unusual for the field of cosmology. Because much of this sub-field of astronomy is dependent on large uncertainties and assumptions, its “facts” are often disproven or untrustworthy. And while the Big Bang theory itself unquestionably fits the known facts better than any other theory at this time, there remain too many uncertainties to believe in it without strong skepticism.

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Solar system of ancient Earths found

8:49 am

Worlds without end: Using archived Kepler data astronomers have identified a solar system of five Earth-sized exoplanets, orbiting a red dwarf star about 117 light years from Earth.

The paper describes Kepler-444, a star that’s 25 percent smaller than our sun and is 117 light years from Earth. The star’s five known planets have sizes that fall between Mercury and Venus. Those planets are so close to their star that they complete their orbits in fewer than 10 days. At that distance, they’re all much hotter than Mercury and aren’t habitable.

The important detail from this discovery is that the star is very ancient, more than 11 billion years old, which means these planets are that old as well. In other words, planets began forming the same time as the first stars. Which also means that there has been plenty of time in the universe for other intelligent life to form, besides our own.

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Comet 67P/C-G’s coma fluctuates widely

12:57 pm

Climate change: Data from Rosetta has shown that the coma surrounding Comet 67P/C-G’s nucleus varies far more than had been expected by Earth-based observations.

“From a telescope, images of a comet’s atmosphere suggest that the coma is uniform and does not vary over short periods of hours or days. That’s what we were expecting as we approached the comet,” said Dr. Stephen Fuselier, a director in the SwRI Space Science and Engineering Division and the lead U.S. co-investigator for the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis Double Focusing Mass Spectrometer (ROSINA DFMS) instrument. “It was certainly a surprise when we saw time variations from 200 km away. More surprising was that the composition of the coma was also varying by very large amounts. We’re taught that comets are made mostly of water ice. For this comet, the coma sometimes contains much more carbon dioxide than water vapor.”

The variations might be seasonal, or even reflect a variation from day to night.

Expect more news stories about Comet 67P/C-G from Rosetta. The journal Science is today publishing a special section on results from Rosetta.

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A quasar shuts down

10:19 am

Astronomers have identified the first quasar to change its energy output.

Quasars are massive, luminous objects that draw their energy from black holes. Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source. As described in an upcoming edition of the Astrophysical Journal, Yale-led researchers spotted a quasar that had dimmed by a factor of six or seven, compared with observations from a few years earlier.

It is also believed that quasars are the central supermassive black holes at the center of these very distant and ancient galaxies. Knowing how these black holes change can tell us something about the behavior of Sagittarius A*, the generally quiet central black hole in the Milky Way.

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More Earthlike exoplanets found

8:29 am

Worlds without end: Using Kepler astronomers have discovered a red dwarf star 150 light years away with three Earth-like exoplanets, one of which is in the habitable zone.

The three planets are 2.1, 1.7 and 1.5 times the size of Earth. The outermost planet, at 1.5 Earth radii, is the smallest of the bunch and orbits far enough from its host star that it receives levels of light from its star similar to those received by Earth from the sun, said UC Berkeley graduate student Erik Petigura, who discovered the planets Jan. 6 while conducting a computer analysis of the Kepler data NASA has made available to astronomers. He calculated that the three planets receive 10.5, 3.2, and 1.4 times the light intensity of Earth. “Most planets we have found to date are scorched. This system is the closest star with lukewarm transiting planets,” Petigura said. “There is a very real possibility that the outermost planet is rocky like Earth, which means this planet could have the right temperature to support liquid water oceans.”

These planets were found by Kepler in its present reconfigured mission, which once again illustrates the incredible effectiveness of an optical telescope in space. If only we were building some.

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New Hubble images to celebrate its upcoming 25th anniversary

8:46 am

The Space Telescope Science Institute (STScI) that operates the Hubble Space Telescope yesterday released two spectacular new images at the January meeting of the American Astronomical Society.

They also announced new data from Hubble that suggests a major eruption had occurred at the center of the Milky Way about two million years ago.

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More Earthlike exoplanets confirmed

8:28 am

Worlds without end: Astronomers have confirmed from Kepler data the existence of 8 new exoplanets, all capable of having liquid water on their surface, with two more like Earth than any previous discovery.

These findings nearly double the number of known planets in the habitable zone, but researchers are especially excited about two of the new exoplanets: Their size, location, and star type means they could be rocky planets like Earth — which means they could have evolved life as we recognize it.

One of the planets, Kepler-438b, is only 12 percent bigger than Earth in diameter. That means it’s quite likely a rocky planet. Scientists have given it a 70 percent chance. Kepler-442b is a bit bigger at around 33 percent larger than Earth, but still has a 60 percent chance of being rocky.

But while 438b hits the sweet spot in size, 442b has it beat when it comes to distance from the sun. Both planets orbit a small red dwarf star, cooler than Earth’s Sun, but they also orbit more closely. 438b gets 40 percent more light than Earth, which means it has around a 70 percent chance of being able to hold liquid water. But with 66 percent as much light as our own planet, 442b has a 97 percent chance of being in the habitable zone.

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Loose fibers significantly cuts Gaia’s output

5:24 pm

Europe’s Gaia telescope, designed to precisely measure the motions of a billion stars in the Milky Way, will have its accuracy cut in half because of the presence of loose fibers on the telescope’s sun shield that are allowing too much stray light in.

These fibres were spotted on Gaia before launch, but cutting them off was considered too risky, because that could allow small particles to enter the spacecraft. Another option, taping them down, was also ruled out because the increased stiffness could prevent the sunshield from unfolding.

The stray light shouldn’t affect measurements of the galaxy’s brightest stars, says Gaia science team member Anthony Brown at the Leiden Observatory in the Netherlands, but it will double the expected errors on most of the stars in the Milky Way, which are much fainter.

For astronomers this is a great tragedy. Gaia will still teach us much, just not as much as they had hoped.

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Kepler reborn

9:54 am

Kepler detects its first exoplanet after its mission was reshaped because of the failure of two of its four gyros.

The newfound planet, HIP 116454b, has a diameter of 20,000 miles, two and a half times the size of Earth. HARPS-N showed that it weighs almost 12 times as much as Earth. This makes HIP 116454b a super-Earth, a class of planets that doesn’t exist in our solar system. The average density suggests that this planet is either a water world (composed of about three-fourths water and one-fourth rock) or a mini-Neptune with an extended, gaseous atmosphere.

This close-in planet circles its star once every 9.1 days at a distance of 8.4 million miles. Its host star is a type K orange dwarf slightly smaller and cooler than our sun. The system is 180 light-years from Earth in the constellation Pisces.

Even more cool, the detection took place during Kepler’s first test run in its new configuration. This bodes well for the space telescope’s ability to make future discoveries.

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Europe approves construction of giant telescope

9:17 am

Europe has approved the construction of the European Extremely Large Telescope (E-ELT), which when completed will be the largest ground-based telescope.

The E-ELT will have a mirror 39 meters across, almost four times bigger than the world’s largest telescope today.

A word to the wise: This very month Sky & Telescope’s cover article, written by yours truly, describes the many difficulties the world’s present generation of giant telescopes have faced. Four out of five have not produced the science promised. Two of the four were dogged by so many technical problems that they required complete reconstruction. The builders of E-ELT will face even greater engineering challenges. Do not be surprised if this telescope does not get completed by 2025 as promised, and even if it does, do not be surprised if it takes another half decade or more before the engineers work out all the kinks.

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Looking down a comet’s neck

2:09 pm

Looking down Comet 67P/C-G's neck

Because all the focus in past two weeks has been on the attempt to land Philae on the surface of Comet 67P/C-G, no one has been paying much attention to the images that Rosetta has continued to produce. On the right however is a humdinger, released on November 17. The image looks into the neck or saddle of the comet, from the side. The giant boulder Cheops can be seen in the saddle, with a jet visible against the black sky above it.

What I like about this image is that I can imagine hiking up the sandy slope to this narrow saddle, where I could stand next to Cheops and look out at that jet. For the explorer in all of us this sure wets the appetite for the future. If only people could go and do that now!

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The best image yet of the birth of a solar system

8:43 am

HL Tau

The new ground-based telescope ALMA has taken an amazing image of a baby star and the planet-forming accretion disk that surrounds it.

ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star. “These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.

ALMA has just been completed and is only in its initial shake-out period. It is also not an optical telescope, but observes in longer wavelengths above infrared. Thus, it can peer through dust clouds to see details like this. And these details confirm that the most accepted theory of planetary formation appears to be right.

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How a big impact gave Vesta its grooves

3:30 pm

New data suggests that when a large impact hit Vesta’s Rheasilvia basin sometime in the past, the entire asteroid was shaken up, producing ripples that eventually surfaced as the giant grooves that circle the asteroid’s equator.

“Vesta got hammered,” said Peter Schultz, professor of earth, environmental, and planetary sciences at Brown and the paper’s senior author. “The whole interior was reverberating, and what we see on the surface is the manifestation of what happened in the interior.”

The research suggests that the Rheasilvia basin on Vesta’s south pole was created by an impactor that came in at an angle, rather than straight on. But that glancing blow still did an almost unimaginable amount of damage. The study shows that just seconds after the collision, rocks deep inside the asteroid began to crack and crumble under the stress. Within two minutes major faults reached near the surface, forming deep the canyons seen today near Vesta’s equator, far from the impact point.

Essentially, for a very very short period of time, immediately after the impact, the solid material of the asteroid acted more like a liquid, producing ripples that immediately settled down as the solid deep equatorial grooves we see today.

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G2 survives Milky Way center fly by

3:08 pm

The uncertainty of science: The gas cloud, dubbed G2, that was going to be eaten by the supermassive black hole at the center of the Milky Way as it did a close fly-by this summer has instead turned out to be a massive star formed when the star’s of its binary system merged.

G2 survived the fly-by, produced no big fireworks which were what was predicted if it has been a gas cloud. The data now suggests that the object is instead a very big star formed when two stars merged.

Massive stars in our galaxy, [astronomer Andrea Ghez] noted, primarily come in pairs. When the two stars merge into one, the star expands for more than one million years “before it settles back down,” Ghez said. “This may be happening more than we thought; the stars at the center of the galaxy are massive and mostly binaries. It’s possible that many of the stars we’ve been watching and not understanding may be the end product of a merger that are calm now.”

Be warned that this new hypothesis about G2 has its own uncertainties. Better data might eventually find it to be something else again.

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Rosetta gets in position to release Phalae

9:36 am

Rosetta has successfully maneuvered into position prior to releasing Philae on November 12 for landing on Comet 67P/C-G.

The thruster burn took place starting at 02:09:55 UTC (03:09:55 CET), ran for 90 seconds and, based on an initial analysis of spacecraft radiometric data, delivered a delta-v – change in speed – of 9.3 cm/sec, as confirmed by the Rosetta Flight Dynamics team. It was the second and final of two ‘deterministic’ (i.e. direction and thrust are prepared in advance) manoeuvres that moved Rosetta onto the planned lander delivery orbit, now at a height of about 30 km, which will be maintained right up until the pre-delivery manoeuvre at two hours before separation at 08:35 UTC (09:35 CET) on the morning of 12 November.

…[T]he next planned orbit-changing manoeuvres will occur on the 12th at (a) 2 hours before separation and (b) about 40 minutes after, in between which Philae will be released. The pre-delivery manoeuvre will shift Rosetta’s trajectory so that the orbiter would be on a path so as to pass over the comet at a distance of 5 km, while the separation will occur at 08:35 UTC on board the spacecraft about 22 km (the confirmation signal will arrive on Earth at 09:03 UTC).

Since Philae is a passive lander, firing no thrusters but simply being thrown gently at the comet by Rosetta, the last two burns are crucial. The first literally puts Rosetta on the same collision course as Philae so that when the lander is released it is on a course to hit the comet. The second takes Rosetta out of that collision course, since no one wants it to hit the comet also.

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Avalanches on an asteroid

9:12 am

A new analysis predicts that when the asteroid Apophis flies past the Earth in 2029, the close fly-by will cause avalanches on the asteroid.

If asteroids pass close to Earth, they begin to experience the effects of our planet’s gravity. Just like the moon pushes and pulls the oceans, creating the tides, asteroids are susceptible to tidal forces from our planet. To judge what effect this will have on Apophis, scientists need to know what it’s made of. Their best guess is based on photos taken by a Japanese spacecraft named Hayabusa, which took detailed pictures of an Apophis-sized asteroid named Itokawa. Those images revealed that the asteroid wasn’t a solid mass of rock spinning through space, but rather a giant clump of debris held together loosely by gravity. “You look at the [Hayabusa] pictures and you’re like, ‘Uh, that’s a pile of rocks, dude.’ It’s very likely that Apophis is similar,” says astrophysicist Derek Richardson of the University of Maryland, College Park.

To show that Earth’s gravity could cause some of these rocks to tumble, Richardson and his colleagues developed a computer model that allowed them to place virtual sand piles across the surface of a model asteroid with roughly the same dimensions as Apophis. By factoring in the gravity from the asteroid, the tidal force from Earth, centrifugal force caused by the asteroid’s rotation, inertial forces, and other effects, the team was able to predict how the particles on the surface of the asteroid would behave on approach. The results confirm that Earth’s tidal forces would be strong enough to cause tiny avalanches on the asteroid, the team reported online ahead of print in Icarus.

Need I note that there are a lot of uncertainties here? Because they are using what is known about a different asteroid, all of their assumptions about Apophis’s properties in their computer model could be very wrong.

Still, this is interesting, because it does demonstrate that an asteroid could be significantly disturbed simply by flying past a planet.

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Comet 67P/C-G smells!

5:07 pm

Instruments on Rosetta have determined that the various molecules coming off Comet 67P/C-G have a strong aroma.

You might expect a rock that spends all its time in a vacuum to be fairly inoffensive, but in fact exposure to sunlight is causing it to give off quite an aroma: hydrogen sulfide, ammonia, formaldehyde, hydrogen cyanide, and other caustic gases would make it smell “suffocating,” like a cross between a filthy barn, an embalming room, and a rotten egg.

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Increasing activity at Comet 67P/C-G

8:49 am

Data from Rosetta in the past month has been showing a steady and gradual increase in dust emissions from the surface.

While images obtained a few months ago showed distinct jets of dust leaving the comet, these were limited to the ‘neck’ region. More recently, images obtained by Rosetta’s scientific imaging system, OSIRIS, show that dust is being emitted along almost the whole body of the comet. Jets have also been detected on the smaller lobe of the comet. “At this point, we believe that a large fraction of the illuminated comet’s surface is displaying some level of activity,” says OSIRIS scientist Jean-Baptiste Vincent from the Max Planck Institute for Solar System Research (MPS) in Germany.

The last two images at the link compare the same location with one image overexposed to make the jets visible. What is interesting is that the source of the jet is not evident in the other normally exposed image. It is almost as if surface material is simply heating up and then using that extra energy to simply throw itself off the surface. Why that then forms jets however is puzzling.

More info here.

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