Interstellar 5

[Antionette Eastin]

Anewly discovered comet has excited the astronomical community this week because it appears to have originated from outside the solar system. The object - designated C/2019 Q4 (Borisov) - was discovered on Aug. 30, 2019, by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. The official confirmation that comet C/2019 Q4 is an interstellar comet has not yet been made, but if it is interstellar, it would be only the second such object detected. The first, 'Oumuamua, was observed and confirmed in October 2017.

The new comet, C/2019 Q4, is still inbound toward the Sun, but it will remain farther than the orbit of Mars and will approach no closer to Earth than about 190 million miles (300 million kilometers).

After the initial detections of the comet, Scout system, which is located at NASA's Jet Propulsion Laboratory in Pasadena, California, automatically flagged the object as possibly being interstellar. Davide Farnocchia of NASA's Center for Near-Earth Object Studies at JPL worked with astronomers and the European Space Agency's Near-Earth Object Coordination Center in Frascati, Italy, to obtain additional observations. He then worked with the NASA-sponsored Minor Planet Center in Cambridge, Massachusetts, to estimate the comet's precise trajectory and determine whether it originated within our solar system or came from elsewhere in the galaxy.

"The comet's current velocity is high, about 93,000 mph [150,000 kph], which is well above the typical velocities of objects orbiting the Sun at that distance," said Farnocchia. "The high velocity indicates not only that the object likely originated from outside our solar system, but also that it will leave and head back to interstellar space."

Currently on an inbound trajectory, comet C/2019 Q4 is heading toward the inner solar system. On Oct. 26, it will pass through the ecliptic plane - the plane in which Earth and the other planets orbit the Sun - from above at roughly a 40-degree angle.

C/2019 Q4 was established as being cometary due to its fuzzy appearance, which indicates that the object has a central icy body that is producing a surrounding cloud of dust and particles as it approaches the Sun and heats up. Its location in the sky (as seen from Earth) places it near the Sun - an area of sky not usually scanned by the large ground-based asteroid surveys or NASA's asteroid-hunting NEOWISE spacecraft.

C/2019 Q4 can be seen with professional telescopes for months to come. "The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020," said Farnocchia. "After that, it will only be observable with larger professional telescopes through October 2020."

Observations completed by Karen Meech and her team at the University of Hawaii indicate the comet nucleus is somewhere between 1.2 and 10 miles (2 and 16 kilometers) in diameter. Astronomers will continue collect observations to further characterize the comet's physical properties (size, rotation, etc.) and also continue to better identify its trajectory.

The Minor Planet Center is hosted by the Harvard-Smithsonian Center for Astrophysics and is a sub-node of NASA's Planetary Data System Small Bodies Node at the University of Maryland. JPL hosts the Center for Near-Earth Object Studies. All are projects of NASA's Near-Earth Object Observations Program and elements of the agency's Planetary Defense Coordination Office within NASA's Science Mission Directorate.

This revolutionary mission includes a suite of 10 instruments that work together to resolve fundamental scientific questions about the local interstellar medium, the boundaries that surround our solar system, and how particles are accelerated to high energies in space.

IMAP offers wide-ranging and groundbreaking opportunities for scientific discovery. For example, IMAP reveals how cosmic raysCharged atomic particles moving in space with very high energies (the particles travel close to the speed of light); most originate beyond the solar system, but some of low energy are produced in solar flares. are filtered by the heliosphereThe region around the Sun where the solar wind dominates over the interstellar medium.. These particles pose risks to astronauts and technological systems. They may even play a role in the formation and presence of life itself in the universeThe totality of all space and time; all that is, has been, and will be..

[This video has no sound] Welcome to the 24-hour livestream video feed from inside the clean room at the Johns Hopkins Applied Physics Lab in Laurel, Maryland, where the IMAP spacecraft is being assembled. This is a LIVE behind-the-scenes look at the integration and testing (I&T) for the spacecraft.

As a self-proclaimed "space nerd," Bianca relishes in the opportunity to champion the Adler's mission to the public every day. In her free time, she enjoys eating Popeyes' $5 Bonafide Box, attending indie-music shows, and checking out all of the world-class museums that Chicago has to offer.

Image Caption: An example of nebulae (and the interstellar medium) can be found in this picture of the Pleiades, an open cluster consisting of approximately 3,000 stars at a distance of 400 light-years (120 parsecs) from Earth in the constellation of Taurus. Image Credit: NASA, ESA, AURA/Caltech, Palomar Observatory

For comparison, the air we breathe has approximately 10 million trillion molecules per cubic centimeter, while some of the lowest density areas of the interstellar medium consists of approximately .1 atoms per cubic centimeter.

While many nebulae form as a result of the gas that is already in the interstellar medium, they can also form after the death of a star. These types of nebulae can be broken down into planetary nebulae and supernova remnants.

You see, a supernova is the biggest explosion in the Universe! They occur when a massive star (much more massive than our Sun) runs out of fuel and thus can no longer fight against the forces of gravity. The expanding cloud of hot gas that results from this explosion is a supernova remnant.

These celestial objects form in high density regions of nebulae called knots. As these regions become more and more dense, gravity takes over and the matter collapses, forming protostars and other celestial objects like planets and comets!

Simply put, the interstellar medium is the material which fills the space between the stars. Many people imagine outer space to be a complete vacuum, devoid of any material. Although the interstellar regions are more devoid of matter than any vacuum artificially created on earth, there is matter in space. These regions have very low densities and consist mainly of gas (99%) and dust. In total, approximately 15% of the visible matter in the Milky Way is composed of interstellar gas and dust.

Approximately 99% of the interstellar medium is composed of interstellar gas, and of its mass, about 75% is in the form of hydrogen (either molecular or atomic), with the remaining 25% as helium. The interstellar gas consists partly of neutral atoms and molecules, as well as charged particles, such as ions and electrons. This gas is extremely dilute, with an average density of about 1 atom per cubic centimeter. (For comparison, the air we breathe has a density of approximately 30,000,000,000,000,000,000 molecules per cubic centimeter.) Even though the interstellar gas is very dilute, the amount of matter adds up over the vast distances between the stars. The interstellar gas is typically found in two forms:

The cold clouds of neutral or molecular hydrogen are the birthplace of new stars if they become gravitationally unstable and collapse. The neutral and molecular forms emit radiation in the radio band of the electromagnetic spectrum.

The ionized hydrogen is produced when large amounts of ultraviolet radiation are released by hot newly-formed stars. This radiation ionizes the surrounding clouds of gas. Visible light is emitted when electrons recombine with the ionized hydrogen, which is seen as beautiful red colors of emission nebulae. Examples of emission nebulae are the Trifid Nebula or the Orion Nebula (seen in this photograph).

Interstellar dust is not like the dust that you might find under your bed; it is made of very different substances. These dust particles are extremely small, just a fraction of a micron across, which happens to be approximately the wavelength of blue light waves. The particles are irregularly shaped, and are composed of silicates, carbon, ice, and/or iron compounds.

When light from other stars passes through the dust, a few things can happen. If the dust is thick enough, the light will be completely blocked, leading to dark areas. These dark clouds are known as dark nebulae. The Horsehead Nebula, seen to the left, is an example of this.

Light passing through a dust cloud may not be completely blocked, although all wavelengths of light passing through will be dimmed somewhat. This phenomenon is known as extinction. The extinction is caused by the light being scattered off of the dust particles out of our line of sight, preventing the light from reaching us. The amount that the light is dimmed depends upon a few factors, including the thickness and density of the dust cloud, as well as the wavelength (color) of the light.

Because of the size of the dust particles, scattering of blue light is favored. Therefore, less of the blue light reaches us, which means that the light that reaches us is more red than it would have been without the interstellar dust. This effect is known as interstellar reddening. (Note that this is not the same thing as redshift, which is due to the effects of relative movement between a light source and its receiver.) This process is similar to those that make the sun red at sunset. (To see an explanation of extinction and interstellar reddening that is more mathematical, please visit this site.) In turn, a dust cloud that is illuminated by star light, when viewed from the side, appears blue, as in the close-up of the "Egg Nebula" seen at right. This is similar to the blue sky we see, which is produced by sunlight scattered by the Earth's atmosphere.

3a8082e126