Tuesday, 30 June 2015

The Universe - The Hubble Deep Field

The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope.

Almost all of the 3,000 objects in the image are galaxies, some of which are among the most distant known.

The Hubble Space Telescope has now been used to produce other similar images of other parts of the sky, some of even smaller areas at greater depth.

Sunday, 28 June 2015

The Universe - Dirty Snowballs

The astronomer Frank Whipple created the description of comets as 'dirty snowballs'.

Comets go around the Sun in a highly elliptical orbit. 

They can spend many years out in the depths of the solar system before they return to the Sun. 

 Comet Hyakutake (1996)

As they come closer to the Sun, the warming of the surface causes materials to melt and vapourise, producing the tail. 

Comet tails can be as long as the distance between the Earth and the Sun.

The tail always points away from the Sun.

Saturday, 27 June 2015

The Universe - The Seager Equation

Professor Sara Seager is an expert on the search for exoplanets.
Professor Seager has revised the Drake equation, to focus on the presence of any alien life, rather than civilisations.

The Seager Equation can be used to estimate how many planets with detectable signs of life might be discovered in the coming years. 

The Seager equation looks like this:


N = the number of planets with detectable signs of life
N* = the number of stars observed
F= the fraction of stars that are quiet
FHZ = the fraction of stars with rocky planets in the habitable zone
FO = the fraction of those planets that can be observed
FL = the fraction that have life
FS = the fraction on which life produces a detectable signature gas

The Drake Equation assesses our chances of finding radio-capable civilizations.

Friday, 26 June 2015

The Universe - The Drake Equation

How hard is it to calculate the probability of humanity communicating with other civilisations?

Dr Frank Drake’s Equation is one attempt to find an answer.

Possibly the most interesting factor is "L", the time a civilization might spend indicating its presence. 

This can be inferred by looking not at the stars, but ourselves.

The longer that humanity succeeds in not annihilating itself and continuing to broadcast detectable signals, the longer we can guess other civilizations will do the same.

More recently, Dr Claudio Maccone has tried to add numbers to the Drake Equation.

Thursday, 25 June 2015

The Universe - Arcturus

Arcturus is a spectacular star, easily found by using the 'Big Dipper' of Ursa Major as a pointer.

Arcturus is an orange-red giant star.

It is the brightest star in the constellation Bo├Âtes (the Herdsman). 

Arcturus is also among the brightest stars that can be seen from Earth.

it has stopped fusing hydrogen in its core as the sun does, and it is now starting to fuse heavier elements such as carbon.

Wednesday, 24 June 2015

The Universe - Leo

The constellation Leo, the lion, is a constellation that does look like its namesake. 

A backward question mark represents the head and mane.

A triangle of stars to the lower left forms the lion's hindquarters and tail. 

Leo's brightest star is the giant, blue-white Regulus, one of the brightest stars in the night sky. 

Regulus is about 79 light-years away. 

The lion's tail is marked by another bright star, Denebola.

Tuesday, 23 June 2015

The Universe - Little Green Men

In 1967, Jocelyn Bell was doing research in radio astronomy at Cambridge University under advisor Anthony Hewish. 

She unexpectedly detected regular radio pulses from the sky with a period of about 1.3 seconds.

Bell and Hewish were astounded by the regularity of the pulses.

They jokingly wondered if the signals were the first transmissions received from an advanced alien civilization. 

They named the first four of these strange sources of radio signals LGM 1, LGM 2, LGM 3, and LGM 4, with LGM standing for "Little Green Men".

These pulsars are actually rapidly spinning neutron stars.

These incredibly dense objects -- about 10 trillion times denser than a lead brick, with more mass than the sun -- produce gravity 100 billion times stronger than Earth. 

A powerful magnetic field traps and accelerates charged particles.

Radio waves are beamed in a cone shape through space, like the rotating light from a lighthouse beacon. 

If Earth lies in the sweep of the beam, we receive the signal once each rotation.

Monday, 22 June 2015

The Universe - The Summer Triangle

The "Summer Triangle" is a feature of the northern hemisphere night sky in summer. 

It is not a constellation. The Summer Triangle is an asterism.

It is formed by the brightest stars of three different constellations.

Vega - otherwise called Alpha Lyrae

Deneb - Alpha Cygni

Altair - Alpha Aquilae

Sunday, 21 June 2015

The Universe - Summer Solstice and the Nebra Sky Disc

A solstice happens when the Sun in the sky is at its furthest point from the celestial equator. 

On the June solstice it reaches its northernmost point, and the Earth’s North Pole tilts towards the sun, at about 23.5 degrees. 

Apart from the well-known links between the solstice and ancient stone structures, another extraordinary ancient object has connections to this celestial phenomenon.

The Nebra Sky Disc is a 3,600-year-old bronze disc which, according to UNESCO, features "the oldest concrete depiction of cosmic phenomena worldwide."  

The disc is such an extraordinary piece that it was initially believed to be a forgery.

The Nebra Sky Disc was discovered in 1999 by two amateur treasure hunters illegally using a metal detector in Ziegelroda Forest, Saxony-Anhalt, Germany.  

It had been ritually buried in a prehistoric enclosure atop a hill (the Mittelberg), along with two precious swords, two axes, two spiral arm-rings and one bronze chisel.

Saturday, 20 June 2015

The Universe - Pluto and its moons

Pluto is a long way away, and until recently these were the best pictures of this distant object.   

That will change in July 2015, when the New Horizons space-probe finally arrives at Pluto. 

Pluto has moons, the largest is called Charon.

New Horizons was launched in 2006.

After touring the Pluto system, New Horizons will fly farther away from the Sun. 

It will enter the zone of space known as the Kuiper Belt to examine some of the icy mini-worlds in that vast region beyond Pluto's orbit. 

Friday, 19 June 2015

The Universe - Venus

The planet Venus is covered with thick clouds.

Unlike Earth’s atmosphere, which is composed mainly of nitrogen and oxygen, Venus’ atmosphere is a dense mix of carbon dioxide and sulphur dioxide gas.

These gases in high concentrations cause a catastrophic greenhouse effect that traps sunlight and prevents it from radiating into space. 
This causes a surface temperature of around 470 K (197 °C).

ESA’s Venus Express has found the best evidence yet for active volcanism on the planet.

Thursday, 18 June 2015

The Universe - New research on habitable exoplanets

The Earth is, of course, a planet orbiting the Sun.

Exoplanets are planets of stars other than the Sun.

There are likely to be hundreds of billions of Earth-like planets in our galaxy which might support life.

The Goldilocks Zone is a band of space where liquid water can exist.

Too near the star, or too far, is bad for life.

In the case of the Sun, Venus lies inside the inner edge of the Goldilocks Zone.

Mars lies at the outer edge.

Tuesday, 16 June 2015

The Universe - Mercury

Mercury is the planet closest to the Sun.  Even so, it is 58 million kilometres away from the Sun.

Mercury orbits round the Sun, but its orbit of the Sun lasts for only 88 days.

Mercury is a small planet.  

Its diameter is only 3100 miles, or 4990 kilometres.  

In many ways it resembles the Moon, with dark and light areas, and many craters caused by impacts.

Monday, 15 June 2015

The Universe - Henrietta Leavitt and the discovery of Cepheid Variable Stars.

Distances in space were largely a mystery at the start of the 20th century.

The distances of some stars had been measured using a method called 'parallax'.

Finding distances of objects far out in space needed a new discovery.

The person who made that discovery was Henrietta Leavitt.

She discovered that certain types of variable stars changed brightness in a regular way.

These pulsating stars are known as Cepheid variables, named after the star Delta Cephei. 

Henrietta Leavitt looked at large numbers of these stars in a feature called the Small Magellanic Cloud, and discovered that brighter Cepheids pulsed more slowly than dimmer ones.

So Cepheids act as 'standard candles'.

Measuring a Cepheid's 'pulsation time' tells astronomers how bright it really is.

By comparing the 'true brightness' with how bright it appears, they can work out how far away it is.                      

Sunday, 14 June 2015

The Universe - Titan

Saturn's biggest moon, Titan, has an atmosphere and lakes.

However, they are very different to those we know on Earth. 

Titan's surface is shaped by rivers and lakes of liquid ethane and methane (the main component of natural gas).

Methane and ethane makes clouds and rain, as water does on Earth. 

There may be volcanoes,but with liquid water as the lava!

Titan is an extraordinary place.

Saturday, 13 June 2015

The Universe - The Pleiades

Orion's Belt points to the red star Aldebaran, and to the Pleiades star cluster. 

The Pleiades can be seen without binoculars, even from light-polluted cities. 

Also known as the Seven Sisters and M45, the Pleiades is an "open star cluster."

The Pleiades contains over 3000 stars, is about 400 light years away, and is 13 light years across. 

The photograph also shows the blue reflection nebulae (gas clouds) that surround the stars.

Friday, 12 June 2015

The Universe - Martian Volcanoes

Mars is smaller than Earth, but some things are familiar.

In this photograph, the great canyon called 'Mariner Valley' is clear.

There are a number of round features, which are volcanoes.

One of the Martian volcanoes, Olympus Mons, is the biggest volcano in the solar system.

Olympus Mons is a shield volcano. 

It is 624 km (374 miles) in diameter. 

That's about the same size as France, or the state of Arizona

Olympus Mons is 25 km (16 miles) high

Its base is encircled by a 6 km (4 miles) high cliff. 

A crater 80 km (50 miles) wide is located at the summit of Olympus Mons. 

In comparison, the largest volcano on Earth is Mauna Loa on Hawaii.

Mauna Loa is also a shield volcano, 10 km (6.3 miles) high and 120 km (75 miles) across. 

The volume of Olympus Mons is about 100 times larger than that of Mauna Loa. 

Thursday, 11 June 2015

The Universe - Jupiter and the Galilean Moons

The planet Jupiter has been known ever since anyone looked at the sky.

It is a bright object which moves slowly across the starry background, taking about 12 years to track all the way around.

Through a telescope it looks spectacular, and even better in pictures taken by space probes.

In this picture, the coloured belts of clouds are clear, with a black shadow of one of Jupiter's moons.

Small telescopes show four moons, but there are also lots of smaller moons orbiting Jupiter.

The four larger moons were first seen by Galileo when he first used a newly-invented telescope in 1610, so they are called the Galilean moons.

The four Galilean moons were just small fuzzy objects until space probes visited Jupiter and showed that they are all different.

 Io has active volcanoes, Europa has an icy crust which may cover an ocean, Ganymede and Callisto are made of rock and ice, but Callisto has far more craters.   

Wednesday, 10 June 2015

The Universe - The Orion Nebula

The Orion Nebula is a fuzzy area among the stars of Orion's sword, which is seen below the three Belt Stars.

To the naked eye, it looks like a star in the sword.

With binoculars or a telescope, it is actually a large glowing cloud of material. 

This nebula is about 1630 light years away. 

Many newborn stars shine on the gas cloud that they collapsed from.

This makes the gas glow.

Tuesday, 9 June 2015

The Universe - Orion the Hunter

The constellation Orion dominates the southern sky during winter in the Northern Hemisphere.

The brightest stars of Orion have wonderful names.

The Red Giant star Betelgeuse marks one shoulder, the other shoulder is marked by Bellatrix.

The three Belt Stars (left to right) are Alnitak, Alnilam and Mintaka.

The knees are marked by Saiph and the very bright Rigel.

Like many star names they are of Arabic origin.

The stars of Orion act as signposts to other stars seen at the same time of year.

The stars shown here are good examples of some of the variety of types of stars.


The Sun is really rather small compared to many stars

Monday, 8 June 2015

The Universe - Professor Carolyn Porco - Saturn's greatest fan

Carolyn Porco's career has involved studying the results of space missions to the outer planets.

Starting with the Voyager probes in the 1980s, she became head of the Imaging Team for the Cassini Saturn mission, and part of the team for the New Horizons probe to Pluto.

In this video, Professor Porco explains why she can't get enough of Saturn.

Sunday, 7 June 2015

The Universe - Saturn's Rings

Saturn's rings are made of chunks of ice, orbiting around the planet.

The gaps are made by the gravity of Saturn's moons pulling on the ring fragments.

To see how thin the rings really are, this picture of Saturn shows the rings edge-on, with Saturn's biggest moon Titan.

Many pictures of Saturn and its moons have been sent back to Earth by the Cassini probe.

Saturday, 6 June 2015

The Universe - Stardust from Exploding Stars

    In 1054, Chinese astronomers saw a brilliant new star.
    They described it as six times brighter than the planet Venus.
    This "guest star," as the Chinese called it, was so bright that people saw it in the sky during the day for almost a month. 

When telescopes were able to investigate the area of the sky where the 'guest star' had been seen, there was a glowing gas cloud.

The remains of the star were named the Crab Nebula, a cloudy, glowing mass of gas and dust about 7,000 light-years away from Earth.

This type of explosion is called a supernova and happens when the star collapses.

Heavy elements are made in supernova events, and those elements are then part of the clouds that collect to make new stars and planets.

This is why scientists say "We are stardust".