SPACE/COSMOS
Outer solar system object has an atmosphere but shouldn’t
National Institutes of Natural Sciences
image:
Artist’s conception of this research showing an imagined time sequence as a star passes behind a TNO with an atmosphere.
view moreCredit: NAOJ
A team of professional and amateur Japanese astronomers found evidence for a thin atmosphere around a small body in the outer Solar System. The object is so small that it should not have a sustainable atmosphere, raising questions about when and how the atmosphere formed. Future observations to better characterize the atmosphere will help solve these mysteries.
In the cold reaches of the outer Solar System lie thousands of small objects known as trans-Neptunian objects (TNOs) because they lie outside the orbit of Neptune. A thin atmosphere has been observed around Pluto, the most famous TNO, but studies of other TNOs have yielded negative results. Most TNOs are so cold, and their surface gravity so weak, that they are not expected to retain atmospheres.
But astronomers like to expect the unexpected, so they took advantage of a lucky “natural experiment” to look for an atmosphere around a TNO known as (612533) 2002 XV93. This object, abbreviated as 2002 XV93, has a diameter of approximately 500 km. For reference, Pluto’s diameter is 2,377 km. The orbit of 2002 XV93 is such that, as seen from Japan, it passed directly in front of a star on January 10, 2024. As the star disappears behind 2002 XV93, it might gradually fade, indicating that the light is being attenuated as it passes through a thin atmosphere; or it might suddenly wink out as it slips behind the solid surface of the TNO.
A team of professional and amateur astronomers, led by Ko Arimatsu at NAOJ Ishigakijima Astronomical Observatory, observed the star as 2002 XV93 passed in front of it from multiple sites in Japan. The obtained data are consistent with attenuation by an atmosphere.
Calculations show that the atmosphere found around 2002 XV93 is expected to last less than 1000 years unless it is replenished. So it must have been created or replenished recently. Observations by the James Webb Space Telescope show no signs of frozen gases on the surface of 2002 XV93 that might sublimate to form an atmosphere. One possibility is that some event brought frozen or liquid gases from deep inside the TNO to the surface. Another possibility is that a comet crashed into 2002 XV93, releasing gas that formed a temporary atmosphere. Further observations are needed to distinguish between these two scenarios.
Journal
Nature Astronomy
Method of Research
Observational study
Subject of Research
Not applicable
Article Title
Detection of an atmosphere on a trans-Neptunian object beyond Pluto
Article Publication Date
4-May-2026
Non-rotating early galaxy is a surprise to astronomers
University of California - Davis
Astronomers using the James Webb Space Telescope have made a surprising discovery about a galaxy long, long ago and far, far away: It isn’t rotating.
That’s something only seen in the most massive, mature galaxies that are closer to us in space and time, said Ben Forrest, a research scientist in the Department of Physics and Astronomy at the University of California, Davis, and first author on the paper published May 4 in Nature Astronomy.
“This one in particular did not show any evidence of rotation, which was surprising and very interesting,” Forrest said.
According to current theories, as the first galaxies formed, angular momentum from inflowing gas and the influence of gravity set them spinning.
Over many billions of years, some galaxies, especially those within galaxy clusters, merged with each other multiple times and their combined rotations added to or partly canceled each other. That’s why some galaxies that are closest to Earth (and therefore also relatively recent) can show little overall rotation but a lot of random movement of stars within them.
This process should take an enormously long time, so it’s surprising that galaxy XMM-VID1-2075 had achieved this state when the universe was less than 2 billion years old.
Forrest and colleagues in the MAGAZ3NE (Massive Ancient Galaxies at z>3 NEar-Infrared) survey had previously observed this galaxy with the W.M. Keck observatory in Hawaiʻi.
“Previous MAGAZ3NE observations had confirmed this was one of the most massive galaxies in the early universe, with already several times as many stars as our Milky Way, and also confirmed that it was no longer forming new stars, making it a compelling target for follow-up observations,” Forrest said.
Pushing the frontiers
The team used the James Webb Space Telescope to take a closer look at XMM-VID1-2075 and two other galaxies of similar age. They were able to measure the relative movement of material inside them.
“This type of work has been done a lot with nearby galaxies because they're closer and larger and so you can do these kinds of studies from the ground, but it's very difficult to do with high redshift galaxies because they appear a lot smaller in the sky,” Forrest said. “(James Webb Space Telescope) is really pushing the frontier for these kinds of studies.”
Of the three galaxies they sampled, one is clearly rotating, one is “kind of messy,” and one has no rotation but a lot of random motion, Forrest said. “That’s consistent with some of the most massive galaxies in the local universe, but it was a bit surprising to find it so early on.”
How did this galaxy become a “slow rotator” in less than 2 billion years? One possibility is that it is the result not of multiple mergers, but a single collision between two galaxies rotating pretty much in opposite directions. That idea is supported by the team’s observations.
“For this particular galaxy, we see a large excess of light off to the side. And so that's suggestive of some other object which has come in and is interacting with the system and potentially changing its dynamics,” Forrest said.
The astronomers are continuing to look for other, similar objects in the early universe. By comparing their observations with simulations, they can test theories about galaxy formation.
“There are some simulations that predict that there will be a very small number of these non-rotating galaxies very early in the universe, but they expect them to be quite rare. And so this is one way in which we can test these simulations and really figure out how common they are, and that can then give us information about whether our theories of this evolution are correct,” Forrest said.
Additional coauthors on the paper are: Brian C. Lemaux, UC Davis and Gemini Observatory, Hawaiʻi; Adam Muzzin and Adit H. Edward, York University, Toronto; Danilo Marchesini, Richard Pan and Nehir Ozden, Tufts University; Jacqueline Antwi-Danso, University of Toronto; Wenjun Chang, UC Riverside; M. C. Cooper and Stephanie M. Urbano Stawinski, UC Irvine; Percy Gomez, W. M. Keck Observatory, Kamuela, Hawaiʻi; Lucas Kimmig and Rhea-Silvia Remus, Ludwig-Maximilians-Universität München, Germany; Ian McConachie, University of Wisconsin-Madison; Allison Noble, Arizona State University; and Gillian Wilson and M. E. Wisz, UC Merced.
The work was supported by grants from NASA, the Space Telescope Science Institute and National Science Foundation.
Journal
Nature Astronomy
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
A massive and evolved slow-rotating galaxy in the early Universe
Article Publication Date
4-May-2026
No comments:
Post a Comment