Exploration of galaxies at much greater distances from Earth may now be possible.
How do stars form in distant galaxies? Astronomers have been trying to answer this question for a long time by detecting radio signals emitted by nearby galaxies. These signals, however, become weaker the further a galaxy is from Earth, making them difficult to detect with today’s radio telescopes.
Researchers from Montreal and India have now captured a radio signal from the most distant galaxy so far at a specific wavelength known as the 21 cm line, allowing astronomers to peer into the early universe’s secrets. This is the first time a radio signal of this type has been detected at such a large distance using India’s Giant Metrewave Radio Telescope.
"A galaxy emits different kinds of radio signals. Until now, it’s only been possible to capture this particular signal from a galaxy nearby, limiting our knowledge to those galaxies closer to Earth," says Arnab Chakraborty, a Post-Doctoral Researcher at McGill University under the supervision of Professor Matt Dobbs.
For the first time, the researchers were able to detect and measure the signal from SDSSJ0826+5630, a distant star-forming galaxy. The atomic mass of the gas content of this particular galaxy, according to the researchers, is nearly twice the mass of the visible stars.The team’s detected signal was emitted from this galaxy when the universe was only 4.9 billion years old, allowing the researchers to peer into the early universe’s secrets. "It’s the equivalent of 8.8 billion years in time," says Chakraborty, a cosmologist at McGill’s Department of Physics.
According to the researchers, these observations demonstrate the feasibility of using gravitational lensing to observe distant galaxies in similar situations. It also opens up exciting new possibilities for studying the cosmic evolution of stars and galaxies using existing low-frequency radio telescopes.
Reference: "Detection of H I 21 cm emission from a strongly lensed galaxy at z ∼ 1.3" by Arnab Chakraborty and Nirupam Roy, 23 December 2022, Monthly Notices of the Royal Astronomical Society.
DOI: 10.1093/mnras/stac3696
The Giant Metrewave Radio Telescope was built and is operated by NCRA-TIFR. The research was funded by McGill University and the Indian Institute of Science.
What is slightly larger than our Moon but nearly 1.4 times the mass of our Sun? ZTF J1901+1458, one of the tiniest white dwarf stars ever discovered. A series of ground- and space-based telescopes observed the dying husk of a sun-like star only 133 light-years away.
In a study published in the journal Nature, researchers detail the discovery and characteristics of ZTF J1901+1458, which is so named because it was spotted by the Zwicky Transient Facility, a sky survey using the Palomar Observatory in California that searches space for any objects with sudden changes in brightness. It’s quite an extreme star.
or smaller reach the end of their lives, white dwarfs form. As they run out of fuel, they begin to collapse; but somewhat paradoxically, this initial collapse causes the star to swell to monstrous sizes and become a red giant (like the famous star Betelgeuse ).
This process also causes the star to cool down slightly and its core contract, which releases a massive amount of energy, causing it to grow even larger. However, it begins to lose its outer layers, leaving only an extremely dense core behind. A white dwarf.
The husk of a blown-out star was what the research team saw in the ZTF records. They used data from the European Space Agency’s Gaia satellite, the Keck telescope in Hawaii, and NASA’s Swift observatory to better understand its characteristics. After analyzing J1901+1458, they realized it was special: It was rapidly rotating and appeared to be nearly as massive as a white dwarf can be.
the white dwarf was formed by two stars that danced for billions of years. They both evolved into white dwarfs before merging to form the new, much more massive star.
It has also been described as the smallest white dwarf discovered, but that title might go to another object believed to be a white dwarf, known as RX J0648.0–4418.
So what will happen to the white dwarf now?
"This is highly speculative, but it’s possible that the white dwarf is massive enough to further collapse into a neutron star," said Caiazzo. Usually neutron stars form when huge stars collapse, but it’s speculated that about one in 10 might be formed from the collapse of a white dwarf.
That’s because strange things are happening in a white dwarf’s super-dense core. Caiazzo describes a subatomic process in which electrons are captured and neutrons are formed. As more electrons are removed, the core approaches collapse and eventually becomes a "zombie" neutron star, one of the most unusual and mysterious cosmic bodies in the universe.
"There are so many questions to address," notes Caiazzo.
HS 475 b is a rocky exoplanet roughly the same size as Earth that orbits very close to a small, dim star. And for the first time, researchers are able to study the planet’s atmosphere.
The James Webb Space Telescope has discovered its first new exoplanet, LHS 475 b, an Earth-sized rocky planet. The planet, which is only 41 light-years away, orbits very close to a small, dim star, completing a full orbit in just two days.
The discovery, announced at the American Astronomical Society (AAS) meeting on Wednesday, January 11th, is notable because most exoplanets discovered are large gas giants similar to Jupiter. Most telescopes struggle to detect Earth-like planets because they are much smaller, at less than a tenth of the diameter.
Previous research with NASA’s Transiting Exoplanet Survey Satellite, another space-based telescope launched in 2018 specifically to search for exoplanets, suggested that this system may contain a planetary candidate. Observations made by JWST in August and September 2022 confirmed the planet’s presence.
The fact that JWST detected this planet indicates that it will be able to detect more Earth-like planets in the future. Furthermore, it should be able to detect their atmospheres, which other telescopes are unable to do with planets of this size.
The ultimate goal of much current exoplanet research is to understand the atmospheres of exoplanets. Astronomers must study the atmospheres of planets in order to better understand whether they are habitable, as this can have a significant impact on factors such as surface temperature.
JWST observed two transits of LHS 475 b (in which the planet passes in front of its host star, causing a temporary and very small dip in the star’s brightness), which both confirmed the presence of the planet and allowed the team to calculate its radius.
They also examined its atmosphere using a technique known as transmission spectroscopy, and while they couldn’t confirm what the atmosphere was, they were able to rule out several possibilities. According to the findings, the planet does not have a hydrogen-dominated atmosphere like Jupiter, nor does it have a pure methane atmosphere. It could possibly have a thick carbon dioxide atmosphere like Venus, or it could have no atmosphere at all — having had its atmosphere stripped away by its star.
, the task remains difficult. Because exoplanets are much smaller than stars and reflect much less light, they are rarely directly detected. Instead, astronomers examine host stars for small changes in brightness or motion that indicate the presence of a planet orbiting them.
This summer, the research team plans another JWST observation of the planet, which should help them learn more. And the study demonstrates how effective JWST is for learning about exoplanets:
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