Evolution of Asteroid Study

Asteroid

On 13 April 2029, asteroid 99942 (heretofore known as Apophis) is estimated to come within 18,300 miles of the Earth. This alarming distance is even more shocking when one takes into consideration that modern geosynchronous satellites orbit the Earth at approximately 26,000 miles. Once the shock has cleared, there is another fact you need to take into consideration: astronomers across the globe are tracking Apophis every day. It is currently labeled as a “0” on the Torino Scale. The Torino Scale is used to categorize the likeness of an asteroid impact on Earth. Read More →

NASA Hubble Finds New Neptune Moon

This composite Hubble Space Telescope picture shows the location of a newly discovered moon, designated S/2004 N 1, orbiting Neptune. The black and white image was taken in 2009 with Hubble’s Wide Field Camera 3 in visible light. Hubble took the color inset of Neptune on August 2009. Image Credit: NASA, ESA, M. Showalter/SETI Institute

This composite Hubble Space Telescope picture shows the location of a newly discovered moon, designated S/2004 N 1, orbiting Neptune. The black and white image was taken in 2009 with Hubble’s Wide Field Camera 3 in visible light. Hubble took the color inset of Neptune on August 2009.
Image Credit: NASA, ESA, M. Showalter/SETI Institute

NASA’s Hubble Space Telescope has discovered a new moon orbiting the distant blue-green planet Neptune, the 14th known to be circling the giant planet.

The moon, designated S/2004 N 1, is estimated to be no more than 12 miles across, making it the smallest known moon in the Neptunian system. It is so small and dim that it is roughly 100 million times fainter than the faintest star that can be seen with the naked eye. It even escaped detection by NASA’s Voyager 2 spacecraft, which flew past Neptune in 1989 and surveyed the planet’s system of moons and rings.

Mark Showalter of the SETI Institute in Mountain View, Calif., found the moon July 1, while studying the faint arcs, or segments of rings, around Neptune. “The moons and arcs orbit very quickly, so we had to devise a way to follow their motion in order to bring out the details of the system,” he said. “It’s the same reason a sports photographer tracks a running athlete — the athlete stays in focus, but the background blurs.”

The method involved tracking the movement of a white dot that appears over and over again in more than 150 archival Neptune photographs taken by Hubble from 2004 to 2009.

On a whim, Showalter looked far beyond the ring segments and noticed the white dot about 65,400 miles from Neptune, located between the orbits of the Neptunian moons Larissa and Proteus. The dot is S/2004 N 1. Showalter plotted a circular orbit for the moon, which completes one revolution around Neptune every 23 hours.

The Hubble Space Telescope is a cooperative project between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations. STScI is operated by the Association of Universities for Research in Astronomy Inc., in Washington.

Source: NASA/Goddard Space Flight Center

New Knowledge About Early Galaxies

Galaxy Formation

The early galaxies of the universe were very different from today’s galaxies. Using new detailed studies carried out with the ESO Very Large Telescope and the Hubble Space Telescope, researchers, including members from the Niels Bohr Institute, have studied an early galaxy in unprecedented detail and determined a number of important properties such as size, mass, content of elements and have determined how quickly the galaxy forms new stars. The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society (cited below).

Graphic: Chano Birkelind, Niels Bohr Institute

Quasars are among the brightest objects in the universe and can be used as lighthouses to study the universe between the quasars and Earth. Here researchers have discovered a galaxy that lies in front of a quasar and by studying the absorption lines in the light from the quasar, they have measured the elemental composition in the galaxy in great detail, despite the fact that we are looking approx. 11 billion years back in time.
Graphic: Chano Birkelind, Niels Bohr Institute

“Galaxies are deeply fascinating objects. The seeds of galaxies are quantum fluctuations in the very early universe and thus, understanding of galaxies links the largest scales in the universe with the smallest. It is only within galaxies that gas can become cold and dense enough to form stars and galaxies are therefore the cradles of starsbirths”, explains Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Early in the universe, galaxies were formed from large clouds of gas and dark matter. Gas is the universe’s raw material for the formation of stars. Inside galaxies the gas can cool down from the many thousands of degrees it has outside galaxies. When gas is cooled it becomes very dense. Finally, the gas is so compact that it collapses into a ball of gas where the gravitational compresion heats up the matter, creating a glowing ball of gas – a star is born.

Cycle of stars

In the red-hot interior of massive stars, hydrogen and helium melt together and form the first heavier elements like carbon, nitrogen, oxygen, which go on to form magnesium, silicon and iron. When the entire core has been converted into iron, no more energy can be extracted and the star dies as a supernova explosion. Every time a massive star burns out and dies, it hence flings clouds of gas and newly formed elements out into space, where they form gas clouds that get denser and denser and eventually collapse to form new stars. The early stars contained only a thousandth of the elements found in the Sun today. In this way, each generation of stars becomes richer and richer in heavy elements.

In today’s galaxies, we have a lot of stars and less gas. In the early galaxies, there was a lot of gas and fewer stars.

“We want to understand this cosmic evolutionary history better by studying very early galaxies. We want to measure how large they are, what they weigh and how quickly stars and heavy elements are formed,” explains Johan Fynbo, who has lead the research together with Jens-Kristian Krogager, PhD student at the Dark Cosmology Centre at the Niels Bohr Institute.

Early potential for planet formation

The research team has studied a galaxy located approx. 11 billion years back in time in great detail. Behind the galaxy is a quasar, which is an active black hole that is brighter than a galaxy. Using the light from the quasar, they found the galaxy using the giant telescopes, VLT in Chile. The large amount of gas in the young galaxy simply absorbed a massive amount of the light from the quasar lying behind it. Here they could ‘see’ (i.e. via absorption) the outer parts of the galaxy. Furthermore, active star formation causes some of the gas to light up, so it could be observed directly.

Using the Hubble Space Telescope, researchers have been able to pinpoint the galaxy causing the absorption in the quasar lying behind it. In the image to the left the quasar is seen as the bright source in the center, while the absorbing galaxy, which lies in front of the quasar, is seen to the left and slightly above the quasar. In the image to the right, most of the light from the quasar is removed so the galaxy is seen more clearly. The distance between the center of the galaxy and point were the light from the quasar passes is approx. 20,000 light years, which is slightly less than the distance between the Sun and the center of the Milky Way. Credit: Hubble Telescope

Using the Hubble Space Telescope, researchers have been able to pinpoint the galaxy causing the absorption in the quasar lying behind it. In the image to the left the quasar is seen as the bright source in the center, while the absorbing galaxy, which lies in front of the quasar, is seen to the left and slightly above the quasar. In the image to the right, most of the light from the quasar is removed so the galaxy is seen more clearly. The distance between the center of the galaxy and point were the light from the quasar passes is approx. 20,000 light years, which is slightly less than the distance between the Sun and the center of the Milky Way.
Credit: Hubble Telescope

With the Hubble Space Telescope they could also see the recently formed stars in the galaxy and they could calculate how many stars there were in relation to the total mass, which is comprised of both stars and gas. They could now see that the relative proportion of heavier elements is the same in the centre of the galaxy as in the outer parts and it shows that the stars that are formed earlier in the centre of the galaxy enrich the stars in the outer parts with heavier elements.

“By combining the observations from both methods – absorption and emission – we have discovered that the stars have an oxygen content equivalent to approx. 1/3 of the Sun’s oxygen content. This means that earlier generations of stars in the galaxy had already built up elements that made it possible to form planets like Earth 11 billion years ago,” conclude Johan Fynbo and Jens-Kristian Krogager.

Source: University of Copenhagen – Niels Bohr Institute

Reference:

Jens-Kristian Krogager, Johan P. U. Fynbo, Cédric Ledoux2, Lise Christensen, Anna Gallazzi, Peter Laursen, Palle Møller, Pasquier Noterdaeme, Céline Péroux, Max Pettini, & Marianne Vestergaard (2013). Comprehensive study of a z = 2.35 DLA Galaxy: mass, metallicity, age, morphology and SFR from HST and VLT Monthly Notices of the Royal Astronomical Society, 433 (1) : 10.1093/mnras/stt955

Newborn Stars and their Effect on the Universe

Star Cluster

When galaxies form new stars, they sometimes do so in frantic episodes of activity known as starbursts. These events were commonplace in the early Universe, but are rarer in nearby galaxies. Read More →