Tag: astronomy

More info on Trappist-1 solar system

9:25 am

Astronomers, using ground-based and orbiting telescopes, have obtained more information about the seven Earth-sized exoplanets that orbit the star Trappist-1 forty light years away.

First, a European effort has found that the planets probably all have loads of water.

A new study has found that the seven planets orbiting the nearby ultra-cool dwarf star TRAPPIST-1 are all made mostly of rock, and some could potentially hold more water than Earth. The planets’ densities, now known much more precisely than before, suggest that some of them could have up to 5 percent of their mass in the form of water — about 250 times more than Earth’s oceans. The hotter planets closest to their parent star are likely to have dense steamy atmospheres and the more distant ones probably have icy surfaces. In terms of size, density and the amount of radiation it receives from its star, the fourth planet out is the most similar to Earth. It seems to be the rockiest planet of the seven, and has the potential to host liquid water.

Data from the Hubble Space Telescope has meanwhile found that three of the seven planets do not have hydrogen in their atmospheres, which at first seems to contradict the European data.

The Hubble observations took advantage of the fact that the planets cross in front of their star every few days. Using the Wide Field Camera 3, astronomers made spectroscopic observations in infrared light, looking for the signature of hydrogen that would filter through a puffy, extended atmosphere, if it were present. “The planets are close enough to their host star, and they have very short orbital periods, which means there are lots of opportunities to make observations,” Lewis said.

Although Hubble did not find evidence of hydrogen, the researchers suspect the planetary atmospheres could have contained this lightweight gaseous element when they first formed. The planets may have formed farther away from their parent star in a colder region of the gaseous protostellar disk that once encircled the infant star.

The Hubble results are actually not very significant. They show only that they did not detect hydrogen in the atmospheres of these three exoplanets, which does not mean it isn’t there. Moreover, this Hubble press release appears to have been issued as much to sell the James Webb Space Telescope and to say that Hubble is looking at Trappist-1 also!

I should add that all of these results are very uncertain. We are looking at something that is very small and is also very far away. Any data obtained is certainly not a precise measurement of what is actually there, only a mere hint.

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NASA funds a cubesat-sized ultra-violet telescope

2:50 pm

NASA has funded a cubesat-based ultra-violet telescope to launch in 2021.

SPARCS is a CubeSat built of six cubical units, each about four inches on a side. These are joined to make a spacecraft two units wide by three long in what is termed a 6U spacecraft. Solar power panels extend like wings from one end. “In size and shape, SPARCS most resembles a family-size box of Cheerios,” Shkolnik said.

The spacecraft will contain three major systems — the telescope, the camera, and the operational and science software. Along with Shkolnik, SESE astronomers Paul Scowen, Daniel Jacobs, and Judd Bowman will oversee the development of the telescope and camera, plus the software and the systems engineering to pull it all together. The telescope uses a mirror system with coatings optimized for ultraviolet light. Together with the camera, the system can measure very small changes in the brightness of M dwarf stars to carry out the primary science of the mission.

As I have noted numerous times recently, the space industry is splitting between large manned projects and tiny unmanned ones. While certain unmanned probes will always have to be larger, the ability to build and launch the same capabilities at a smaller size is lowering cost and allowing more probes to be launched.

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NASA renames Swift telescope to honor Neil Gehrels

10:48 am

NASA has renamed the Swift space telescope, designed to quickly detect and observe fast transient events in space like gamma ray bursts, to honor the late Neil Gehrels, the man who led the project from day one.

During a presentation at a NASA town hall meeting at the 231st Meeting of the American Astronomical Society here, Thomas Zurbuchen, NASA associate administrator for science, said that Swift would now be known as the Neil Gehrels Swift Observatory.

Gehrels, who died in February 2017, had been principal investigator for Swift, a mission launched in 2004. The spacecraft was designed to be able to rapidly respond to transient events, such as gamma-ray bursts, observing them at wavelengths ranging from gamma rays to visible light.

“Neil wore many hats in service to the astrophysics community,” said Paul Hertz, director of NASA’s astrophysics division, at a later press conference at the meeting. In addition to being the principal investigator for Swift, had served as project scientist on the Compton Gamma-Ray Observatory and Fermi missions. At the time of his death last year he was project scientist for the Wide-Field Infrared Survey Telescope, NASA’s next flagship astronomy mission after the James Webb Space Telescope.

Knowing astronomers, they will now refer to this observatory as the NGSO. Not I. It will be “Gehrels Swift” to me, whenever I need to mention it. Gehrels was one of the most friendly, open, and easy-to-work-with astronomers I ever had to deal with. He is sorely missed.

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First six segments of Extremely Large Telescope cast

8:23 am

The first six mirror segments of the European Southern Observatory’s Extremely Large Telescope have been successfully cast.

These segments will form parts of the ELT’s 39-metre main mirror, which will have 798 segments in total when completed. The ELT will be the largest optical telescope in the world when it sees first light in 2024.

The 39-metre-diameter primary mirror of ESO’s Extremely Large Telescope will be by far the largest ever made for an optical-infrared telescope. Such a giant is much too large to be made from a single piece of glass, so it will consist of 798 individual hexagonal segments, each measuring 1.4 metres across and about 5 centimetres thick. The segments will work together as a single huge mirror to collect tens of millions of times as much light as the human eye.

The segments must now be cooled, then their surfaces ground and polished to the right shape. If all goes right, they will make more than 900 segments (with about a 130 as spares), manufactured to have the telescope operational by 2024.

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Was the solar system formed inside a giant bubble?

10:28 am

Don’t bet the house on this! Astronomers have come up with a new theory for the formation of the solar system, that it was formed inside a giant bubble inside a Wolf-Rayet star, in order to explain the known ratios of certain isotopes here.

The new theory for how the solar system formed starts with an extremely massive star known as a Wolf-Rayet star. Of all the stars in the universe, these stars burn the hottest. Because they are so hot, they also have exceptionally strong stellar winds.

As a Wolf-Rayet star sheds its outer layers – a normal end-of-life process for a giant star – its strong stellar winds plow through its loosely held cloak of material, forming densely shelled bubbles. According to the study, the solar system could have formed inside of one of these bubbles.

While this theory would explain a number of mysteries about the ratios of aluminum-26 and iron-60 in our solar system, which correspond closer to those in a Wolf-Rayet star than the galaxy itself, it is quite far-fetched. More hard data is necessary, including real evidence of such things actually happening in such stars, before it can be taken very seriously.

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New data from Tabby’s Star suggests that dust, not alien megastructures, is the cause of its dimming

8:39 am

New observations of Tabby’s Star now suggests that it is dust, not alien megastructures, that has caused the star’s erratic fluctuations in dimming over the past century.

“Dust is most likely the reason why the star’s light appears to dim and brighten. The new data shows that different colors of light are being blocked at different intensities. Therefore, whatever is passing between us and the star is not opaque, as would be expected from a planet or alien megastructure,” said [LSU Department of Physics & Astronomy Assistant Professor Tabetha Boyajian].

Though the data appears strong, it still leaves astronomers a bit baffled about how dust could cause the particular dimming they have seen.

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Arecibo returns to operation with images of asteroid Phaethon

10:02 am

The Arecibo Observatory in Puerto Rico has resumed science observations after recovering from Hurricane Maria with new radio images of the asteroid Phaethon.

After several months of downtime after Hurricane Maria blew through, the Arecibo Observatory Planetary Radar has returned to normal operation, providing the highest-resolution images to date of near-Earth asteroid 3200 Phaethon during its Dec. 16 flyby of Earth. The radar images, which are subtle at the available resolution, reveal the asteroid is spheroidal in shape and has a large concavity at least several hundred meters in extent near the leading edge, and a conspicuous dark, circular feature near one of the poles. Arecibo’s radar images of Phaethon have resolutions as fine as about 250 feet (75 meters) per pixel.

The images also revealed that Phaethon, which is considered a potentially hazardous near Earth asteroid, is about 3.6 miles across and is about a half mile larger than previously believed.

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A star that is devouring its planets?

12:55 pm

Astronomers now think that a nearby star that erratically dims inexplicably does so because of clouds of debris left by the destruction of one or more exoplanets.

A team of U.S. astronomers studying the star RZ Piscium has found evidence suggesting its strange, unpredictable dimming episodes may be caused by vast orbiting clouds of gas and dust, the remains of one or more destroyed planets. “Our observations show there are massive blobs of dust and gas that occasionally block the star’s light and are probably spiraling into it,” said Kristina Punzi, a doctoral student at the Rochester Institute of Technology (RIT) in New York and lead author of a paper describing the findings. “Although there could be other explanations, we suggest this material may have been produced by the break-up of massive orbiting bodies near the star.”

Their data also suggest that the star is young.

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The best infrared image yet of a star’s surface

10:34 am

The surface of a star

Astronomers, using the Very Large Telescope in Chile have taken the best infrared image of the surface of a star, revealing gigantic granules or convection cells, across the star’s surface. These cells are somewhat similar to the bubbles you see when you simmer tomato sauce. Our own Sun usually has about two million such cells across its surface. For this aging red giant, which has the same mass as the Sun but has expanded to 350 times its diameter, things are different.

[The astronomers] found that the surface of this red giant has just a few convective cells, or granules, that are each about 120 million kilometres across — about a quarter of the star’s diameter [2]. Just one of these granules would extend from the Sun to beyond Venus.

I have posted the image on the right, reduced slightly in resolution to show here. The press release says that this is the first time that such granules have been imaged, but I think that is a bit of an overstatement. In fact, one of the very first articles I ever wrote, back in 1994, described an infrared image taken of Betelgeuse that showed similar giant bubbles or cells. What makes this image significant is its improved resolution. The ability to see smaller details on the faces of distant stars continues to improve.

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Oumuamua has a thick carbon crust built up by its interstellar travel

8:59 am

New results of observations of the interstellar object Oumuamua suggest that it has a thick crust of organic carbon soot that was slowly built up during the millions of years it traveled between the stars.

New observations of the cigar-shaped body found evidence for a deep surface layer that formed when organic ices – such as frozen carbon dioxide, methane and methanol – that make up the object were battered by the intense radiation that exists between the stars.

…The deep outer crust may have formed on the body over millions or even billions of years and gives ‘Oumuamua a dark red colour, according to researchers who investigated the object with the William Herschel Telescope on La Palma in the Canary Islands and the European Southern observatory in Chile’s Atacama desert.

There have been a slew of news stories today about these results, all focusing not on the crust of the object, which tells us nothing really about its interior, but on one quote by one scientist from the press release, who theorized — based on zero data — that the interior of the object could be icy. From this quote I have seen at least a half dozen stories exclaiming that Oumuamua thus could be like a comet, based on no information at all.

All we have learned is that traveling for a long time in interstellar space causes a build up of carbon-rich materials on the surface of an object. What might be hidden under that crust remains entirely unknown. It could be icy, but we don’t know that.

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Initial analysis of radio observations of Oumuamua detect no artificial signals

1:34 pm

The initial analysis of the first set of radio observations of Oumuamua by Breakthrough Listen has so far not detected any artificial signals.

No such signals have been detected, although the analysis is not yet complete. So far, data from the S-band receiver (covering frequencies from 1.7 to 2.6 GHz) has been processed, and analysis of the remaining three bands is ongoing. A subset of the S-band data is now available for public inspection in the Breakthrough Listen archive3, and additional data will be added as it becomes available.

The data is stored in specialized formats, and analyzing it may be challenging for non-experts. We invite those who are interested to study the tutorial material provided by the Breakthrough Listen science team at the University of California, Berkeley, SETI Research Center and to assist with the analysis not only of this intriguing object, but of the entire Breakthrough Listen dataset.

They still plan three more observation sessions.

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